青海湖湖水性质、颗粒物沉积通量季节和年际变化——来自沉积物捕获器的研究

本文通过在青海湖南盆沉积中心试验性放置的Mark 8-13型时间序列沉积物捕获器所收集到的为期15个月的自然沉降颗粒物，分析了颗粒物沉积通量和物质组成，结合温盐传感器（CTD）所记录湖水参数数据的分析，讨论了青海湖上部10 m左右湖水中所发生沉积作用的季节与年际变化特征及其与环境参数的相互关系。结果表明，采集期间所沉降的总颗粒物具有显著季节和年际变化特征，其平均年沉降通量为112 g·m^-2·yr^-1，其组成主要是自生碳酸盐（高Mg方解石、文石）、生物壳体（介形虫、硅藻等）等内生作用形成的物质，以及少量的碎屑矿物。与实时监测的湖水参数比较表明，具有显著季节和年际变化的青海湖内生物质通量变化主要受控于夏季温度的变化。其沉积机制为：湖水温度的升高，有利于高Mg方解石和文石等自生矿物从碳酸盐过饱和的碱性湖水中结晶沉淀（盐度降低），也有利于藻类和介形虫等微体生物大量繁殖，表现为温度偏高的2010年比2011年具有较低的湖水盐度和高得多的沉积通量。因此，青海湖自生碳酸盐沉淀通量可以用来反映湖水盐度和/或温度的变化，尽管这些内生作用形成的物质可能只约占到湖底沉积物的5%~20%。为更全面地了解青海湖现代沉积过程，有必要在更多点位、不同的深度进行长期放置捕获器和实时监测湖水参数变化。

Seasonal and interannual variations of the lake water parameters and particle flux in Lake Qinghai: A time series sediment trap study

On the basis of fluxes and compositions of time series settling particles collected in situ by a McLane Mark 8-13 sediment trap deployed pilotly at the southern basin center of Lake Qinghai, the sedimentation processes of particles within water column of the upper 10 meters and the relationship of fluxes and compositions with state-of-the-art sensing data of lake water parameters by a CTD (Conductance, Temperature, Depth) were discussed. The results show distinct seasonal and interannual variations of the measured particles between July 2010 and October 2011, with an annual total flux of 112 g·m^-2·yr^-1, whose compositions were mainly authigenic carbonates (high Mg calcite, aragonite), biologic shells (ostracods, diatoms, etc.), both being endogenic formations formed from water column, and some detrital.By correlating with the state-of-the-art sensing lake water data, the particle fluxes of the endogenic formations with distinct seasonal and interannual variations were controlled chiefly by water temperature during summer time. Because Lake Qinghai presently is alkaline and is supersaturated with respect to carbonates, a high temperature favored the precipitation of carbonates (such as high-Mg calcite and aragonite)from super-saturated water and the reproduction of microbiota such as ostracods and diatoms, resulting in a much higher particle flux but a lower salinity in 2010 than in 2011 due to a relatively high temperature in 2010. We suggest that precipitation flux of authigenic carbonates in Lake Qinghai can be used to reflect change of lake water salinity and/or temperature, though these endogenic matters only contribute 5% to 20% of total annual sediment flux. In order to better understand particle processes within Lake Qinghai, it is necessary to long-term deployment of time series sediment traps and to gain state-of-the-art sensing data at various locations and depths.